1. Field of the Invention
This invention relates to modified polymer compositions having carbonyl functions as an integral part of the recurring unit, such as polyamide and polyester compositions, which exhibit improved physical properties. More particularly, this invention relates to such compositions comprising a novel nucleating agent.
2. Brief Description of the Prior Art
Polymers having carbonyl functions as for example polyamide compositions, such as poly(hexamethylene adipamide), poly(caprolactam) and the like, and thermoplastic polyesters, such as poly(ethylene terephthalate), poly(butylene terephthalate) and the like, can be produced on a large scale at relatively low cost, and have found extensive use in the production of molding compositions and fibers. When employing polyamide and polyester compositions for such uses, it is desirable that the compositions possess stable and fine crystalline structures, which usually accompany desirable physical properties. In the prior art, it is known that these desirable physical properties, as well as faster molding cycles and greater productivity in molding operations can be achieved by increasing the rate of crystallization of the molding composition. Various prior art references disclose that increased rates of crystallization involve a process of nucleation in which various kinds of inorganic, organic and polymeric compositions may be employed as nucleation agents. For example, Great Britain Patent No. 1,211,685 and German Pat. No. 1,694,476 disclose that substances such as calcium fluoride, molybdenum disulfide, lead tungstate, antimony trioxide, graphite, talcum and asbestos are effective nucleation agents.